The invention relates to turbine rings for gas turbines, whether industrial gas turbines or gas turbines forming aeroengines.
In a gas turbine, a turbine ring defines a flow section at a rotary wheel of the turbine for a stream of hot gas passing therethrough. In order to ensure the best possible efficiency, it is important to avoid gas passing directly between the tips of the blades of the turbine wheel and the inside surface of the ring. Thus, in the usual way, a turbine ring is provided on its inside face with a layer of abradable material with which the turbine tips can come into contact without significant damage under the effect of dimensional variations of thermal origin or as the result of the centrifugal force that is applied to the blades.
Turbine rings are usually made as a plurality of adjacent sectors of metal material.
For example, document U.S. Pat. No. 6,758,653 proposes replacing the metal material of the turbine ring sectors by a thermostructural composite material, and more particularly by a ceramic matrix composite (CMC) material. Such a material presents mechanical properties that make it suitable for constituting structural elements and also has the ability to conserve these properties at high temperature, while presenting density that is much lower than that of the metal materials commonly used in such an application.
It is therefore attractive to replace the metal material of the turbine ring sectors with a CMC material. Nevertheless, it is necessary to design an assembly for the ring sectors that is rather complex in order to accommodate the difference between the coefficients of expansion of a CMC material and of the material of a metal casing in which the ring sectors are assembled, and while minimizing leaks against adjacent sectors.